1. Field of the Invention
This invention relates to electrically connecting one electronic component to another electronic component and, more particularly, to attaching a BGA module having floating signals to unconnected surface BGA pads on a printed circuit board.
2. Description of Related Art
The use of solder to join materials such as components of an electronic structure is well known in the art. In the electronics area there are a myriad of electronic components which require connection to other electronic components or to other levels of packaging. Examples include mounting of integrated circuit chips to a metallized substrate, multi-layer ceramic substrate (MLC), laminate organic substrate, glass ceramic substrate, card (direct-chip-attach, DCA), printed circuit board (PCB) and any substrate made of composite materials meeting thermal and mechanical properties. This description will be directed to for convenience to second level surface mount technology whereby a ball grid array (BGA) containing component is electrically connected to a printed circuit board.
The term Ball Grid Arrays (BGA""s) refers to a broad class of microelectronic substrate modules that are connected to a board/card by means of an array of solder balls on the module. Such interconnections are first formed by joining solder balls to the substrate module thus creating the BGA. The BGA is subsequently joined to the PCB or card during reflow assembly.
Printed circuit boards (PCB""s) or printed wiring boards (PWB""s) are rigid or flexible single, double or multi-layered boards having printed conductors placed upon or within the board material. A PCB is designed to receive separately manufactured electrical components and to interconnect those components in an overall circuit structure. The joining of such components or parts is well-known in the electronics art.
PCB""s are classified by the number of layers they contain as implied by the terms single-sided, double-sided and multi-layered boards. Multi-layer PCB""s typically have internal interconnected conductor circuits and internal ground or power planes, as well as conductors on both sides of the board. Most industrial and commercial PCB""s are manufactured from rigid copper-clad epoxy-impregnated glass fiber or a phenolic-impregnated laminate. The leads or wires from components to be joined to the board can be surface mounted or connected at plated-through holes at the terminal ends of each conductor. In a multi-layer setting, terminal ends of conductors connect at vias which extend from a buried conductor plan to a surface layer. From the surface layer, each via can be connected to an overlying electrical component by a BGA array.
Assemblies containing a circuit board and a Ball Grid Array (BGA) module typically must undergo modifications or repair. For example, a module to be connected may have an open internal net (typically referred to as a floating signal) that should actually be connected to another net, a reference voltage, supply voltage, or ground potential of a printed circuit board. Furthermore, engineering changes might be necessary once the circuit is in its operating environment. Typically, such circuit boards are discarded and replaced with new boards fabricated to include the modification.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method for electrically connecting one electronic component to another electronic component using solder interconnections, wherein one of the components must be adapted or repaired before component assembly.
It is another object of the present invention to provide a method for connecting a floating signal BGA pad of a component to an internal ground or voltage plane in a printed circuit board to which the component is to be connected.
A further object of the invention is to provide electronic structures made using the solder interconnection structure and method of the invention.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method for connecting a pad on a first electronic component to an internal plane in a second electronic component comprising the steps of:
supplying a first electronic component such as a BGA module containing a plurality of first solder sites for solder connection to a second electronic component;
supplying a second electronic component such as a printed circuit board having a plurality of corresponding second pads for attachment to the first corresponding solder sites of the first electronic component;
forming an opening in the second electronic component from the surface of the second electronic component to an internal plane desired to be connected to the first solder site, the opening being proximate the second pad to be attached to the internal plane of the board;
attaching an electronic connector such as a wire from the internal plane to the second pad, the wire preferably having a higher melting point than the solder sites to be used to make the solder connection between the first and second components; and
solder attaching the first electronic component to the second electronic component.
In a related aspect of the invention an electronic component assembly comprising a first electronic component electronically attached to a second electronic component comprises:
a first electronic component having a plurality of pads and solder connection sites thereon for connection to a second electronic component;
a second electronic component having corresponding pads thereon for attachment to the pads and solder connection sites of the first electronic component;
one or more openings in the second electronic component from the surface of the second electronic component to an internal plane desired to be electrically connected to the first electronic component, the openings being proximate the pads on the second electronic component to be connected to a corresponding pad on the first electronic component;
an electrical connector extending from the opening to the pad and connecting the internal plane of the second electronic component to the pad of the second electronic component; and
the first electronic component and second electronic component pads being connected together by the solder connection sites.